In the field of spinal pathologies, the development of spinal fixation devices represents a major medical breakthrough. Surgically implanted fixation systems are commonly used to correct a variety of back structure problems, including those which occur as a result of trauma or improper development during growth. A commonly applied fixation system includes the use of one or more stabilizing rods aligned in a desired orientation with respect to a patient's spine. Anchoring screws are inserted into the patient's spinal bones, and a series of connectors are used to rigidly link the rods and anchors.
A variety of designs exist, with each design addressing various aspects of the difficulties that arise when one re-shapes an individual's spine to follow a preferred curvature. Known spinal implant systems often correct one set of problems only to create new ones.
Common to all spinal implant systems is the necessity for proper anchoring to the bone so as to provide support for the aforementioned components. While bone screws are commonly used for anchoring, the use of a polyaxial design has proven very effective in allowing a surgeon the flexibility to secure an installation with minimal strain on the individual.
For this and other reasons, screws located in bone structure typically use a polyaxial base and a specially designed connector member for attachment to a component such as an alignment rod. A problem with the current technology is that bone structure cannot be determined until the patient's bone is exposed. This problem requires a large inventory of various sized implants to be on hand during every surgery. The surgeon must search through the inventory to assemble a combination based on his prediction of what will be required. Even if an implant combination is predicted, the anchoring screw may still require angular insertion due to muscle structure or nerve locations. Any movement of muscle and other tissue increases the difficulty of the operation and can be a major trauma to the patient. Still yet, bone condition may require oversize threads to achieve a suitable purchase to the bone. As a consequence, the surgeon must either maintain a large inventory of anchoring devices, or have a vendor standing by with a large inventory of anchoring devices that will hopefully meet the individual requirements.
One of the problems with a polyaxial pedicle screw is the lack of a stabilized angular placement position during installation. Once a polyaxial pedicle screw is inserted into the bone, the connector component portion has yet to receive a connecting rod leaving the connector assembly to flop over making it difficult for the Surgeon to grasp while in the midst of surgery. This problem is compounded by the need to align multiple component heads for receipt of a connecting rod.
Disclosures related to polyaxial pedical screws are exemplified by the following patents; U.S. Pat. Nos. 7,066,937; 7,947,065; 8,075,603; 8,465,065; 6,485,491; 5,133,717; 5,129,900; 4,887,595; 4,946,458; 5,002,542; 4,854,304; 4,887,596; 4,836,196; 5,800,435; 5,591,166; 5,569,247; 5,716,357; 5,129,900; 5,549,608; 6,716,214; 6,565,567; 5,501,684; 4,693,240; 4,483,334; 4,273,116; 6,672,788; 4,708,510; 3,433,510; 7,445,627 and U.S. Publication Numbers 2008/0177322; 2006/0241599; 2006/0235392; 2006/0155277; 2006/0149240; 2003/0118395 and 2008/0269809.